Eyepiece focal lenght ..Did i change it? (1 Viewer)

I have been using an astronomy eyepiece, the BST explorer 12mm,via a home made adapter with my nikon ED50,with excellent results i must say..the eyepiece is made of two separated parts, the main body and a barlow that sits inside the astronomy barrel.If the barrel is unscrewed the barlow stays inside ,although can be easily screwed out.
I know that some of the nikon fieldscope eyepieces are of a similar design, a main eyepiece and a barlow screwed to it
..In the BST 12 mm design the barlow sits a couple mm below the main eyepiece body,leaving a space between the elements,but to be able to adapt the design to the nikon scope,And reach infinity ,i had to fit the eyepiece and barlow close together....
Did i change the eyepiece focal lenght/combo magnification with this small change?...i know that if such change happened it would not be significant because i have tested the eyepiece in a celestron regal ,both with and without the space and i didnt notice much,if any, difference,but im curious about this fact...
Any insight?
Thanls

Yes, you did change the focal length of the eyepiece. Moving the Barlow closer to the other elements increases the effective focal length of the eyepiece, but of course, I don't know by how much in this case.

Baader takes advantage of this effect by supplying different width spacing rings for placement between the Barlow and the other elements in the Hyperion eyepieces.

Henry

Thanks Henry.I thought so,but i wasnt sure if i was increasing or decreasing the Fl...so this means that if my 12 mm has now a longer FL im getting less magnification.I would need to measure the exit pupil carefully,to make sure of the exact figures...